Update dependency zod to v4

Author: renovate[bot]

package.json

@@ -19,7 +19,7 @@
     "cross-env": "^7.0.3",
     "luxon": "^3.5.0",
     "tailwindcss": "^3.4.16",
-    "zod": "^3.23.8",
+    "zod": "^4.0.0",
     "zod-validation-error": "^3.3.1"
   }
 }